COP16: Ecosystems as climate thermometers and recorders of biodiversity impacts

"This is high school science: the temperature at which water freezes and becomes ice is 0 degrees Celsius. Above that, it melts. And if we put a thermometer in Santa Isabel, we see that the constant temperature is between 2 and 5 degrees Celsius. This is a temperature where the glacier clearly has no choice but to melt," says Ceballos.

It is estimated that in the middle of the 19th century, the Santa Isabel glacier covered about 27 square kilometers. One hundred years later, 9.4 square kilometers remained, but the latest calculations by Ideam estimate that there is currently only 0.29 square kilometers of ice. This means that in 70 years, 96% of the ice on this peak has been lost, a situation that has accelerated since 2016 (due to the strong El Niño phenomenon of that year): in eight years, two thirds of the remaining glacier disappeared.

Moreover, it is no longer a single ice sheet, but several fragmented miniglaciers. Two of them (Otún Norte and Otún Sur) became extinct in 2022, and another (Conejeras) disappeared at the beginning of this year. Thus, Santa Isabel went from nine to six "glaciers" in just two years.

According to the expert, we are living in a historical and irreversible moment from which we can only learn. What were once great ice sheets are giving way to the páramo: one ecosystem is dying to make way for another. There is no way to recover it; the snowfalls are less frequent and insufficient, the thaw leaves a thick layer of volcanic ash that makes it even more difficult to compress the crystals and, as Ceballos says, this peak has the altitude against it. At an altitude of less than 5,000 meters, the chances of temperatures falling below 0°C for a sustained period are almost nil.

Ice melts on snow-capped peaks

Santa Isabel is the most dramatic case, but not the only one. In fact, Ideam estimates that by 2100 there will be no snow-capped peaks left in Colombia. Currently, the country's glacier cover is 33 km², only a tenth of what it was in the mid-nineteenth century and half of what it was in the nineties. And it seems incredible how the art of previous centuries (historical records of what these frozen masses were) showed huge Andean peaks adorned in white almost to their skirts.

"Fortunately, in the other five snow-capped peaks in the country (Sierra Nevada de Santa Marta, Sierra Nevada del Cocuy, and the snow-capped volcanoes of Ruiz, Huila, and Tolima), the rest of the glacier layer is above 5,000 meters above sea level, which does not guarantee that they will survive, but they will survive a little longer," says Ceballos. 

But just because they are at that altitude does not mean that they have not suffered the ravages of climate change, especially the El Niño phenomena of 2016 and last year, which have significantly affected the glacier layer.

A clear example is the Sierra Nevada de Santa Marta, which is severely affected by temperature changes in the Caribbean. It is a mystery to scientists because Ideam's instruments cannot reach it because it is sacred indigenous land, so it can only be studied with satellite images. These show that it is losing about 5 percent of its area each year. Today it covers 5.3 km².

The best preserved peak is the Sierra Nevada del Cocuy (also known as Güicán), with 12.8 km² and about 5,400 meters high. It is probably the one that will survive the longest because it has the good fortune to be influenced by the Andean and Orinoco zones, so that while there is a dry season on one side, there is a wet season on the other, making it less susceptible to hot and dry seasons.

This is not the case for the country's three snow-capped volcanoes: Ruiz, Huila and Tolima. Although their altitude favors them, their melting has accelerated in recent years, and they have lost half of their surface area in the last 30 years. The most dramatic case of these three is that of Tolima, whose extension today is barely 0.5 km², surely the next to become extinct after Santa Isabel.

Glaciers, a climate thermometer

"I would say that it is a miracle that we have snow-capped mountains in Colombia," says the glaciologist expert. And indeed, the fact that the country has this type of ecosystem is absolutely unusual.

No wonder. In the world there are only three regions on the equatorial line that have a layer of glaciers. They are Colombia and Ecuador, a small region of Africa (where Mount Kilimanjaro is located), and Indonesia.

And they are so rare in these equatorial zones because the few glaciers that exist there are conditioned by factors such as being in the Intertropical Confluence Zone (characterized by higher temperatures) and a different exposure to solar radiation, not to mention that there are no seasons, no long snow seasons, or constant cold.

As a result, the dynamics of the glaciers as an ecosystem are very different, because unlike in other latitudes, where snow-capped peaks are the source of water, here the water supply depends more on rivers and tributaries that originate in the páramos. And this is encouraging, says Ceballos, because the lack of ice does not imply water scarcity, as is the case in European countries, for example.

This makes the study of glaciers in countries like Colombia different, but no less important. The six small glaciers that Colombia currently has, although relatively insignificant in the global balance of glaciers, but because they are equatorial glaciers, are the "thermometers of the world", a thermal indicator that shows how much the planet is warming, a reminder that if humanity continues on the same path, what is happening today in the Santa Isabel could happen in the Alps, the Andes or the Himalayas.

It is more than the loss of the landscape, it is the loss of an entire ecosystem that, inhospitable as it may seem, is still important for the thermal regulation of the planet.

"We are facing a historic moment. We have no choice but to learn from it, to visit the snow-capped mountains that are still visible, to witness the last of the ice that we have left. Imagine telling your grandchildren that you personally saw ice on the tops of the mountains! Snow in Colombia! How is that possible?" says Ceballos.

He adds: "It is sad that my life's work is disappearing, but just as one ecosystem dies and another is born, a profession disappears, but now more biologists and environmental engineers will be needed to study the effects of this change. For my part, I can say that I lived under the ice in a tropical country and witnessed an event that will go down in history".